1. Field of the Invention
The present invention relates to a heating apparatus with electrostatic attraction function, and more particularly to a wafer heating apparatus with electrostatic attraction function, which is preferably used for a heating process of a semiconductor wafer during a fabrication process of semiconductor devices including a temperature rising process.
2. Description of the Related Art
For heating a semiconductor wafer during a fabrication process of semiconductor devices, a heater in which a metal-wire is wound was used conventionally. However, since there was a problem of metal contamination to a semiconductor wafer when this heater was used, in recent years there has been proposed using a wafer heating apparatus united with ceramics in which a ceramics thin film is used as a heating layer (for example, see Japanese Patent Laid-Open (Kokai) No. 4-124076).
Also, in the case of heating a semiconductor wafer, an electrostatic holding apparatus has been used to fix the semiconductor wafer on a heater in a reducing atmosphere, and its material has been shifted from resin to ceramics as the process has been performed at higher temperature (see Japanese Patent Laid-Open (Kokai) Nos. 52-67353 and 59-124140).
Further recently, there has been proposed a wafer heating apparatus having an electrostatic attraction function, in which the wafer heating apparatus united with ceramics and the electrostatic holding apparatus are combined. For example, in a low temperature range such as an etching process, an apparatus using alumina for an insulating layer of an electrostatic holding apparatus has been used (see New Ceramics (7), pp.49-53, 1994), and in a high temperature range such as a CVD process, an apparatus using pyrolytic boron nitride for an insulating layer of an electrostatic holding apparatus has been used (see Japanese Patent Laid-Open (Kokai) Nos. 4-358074, 5-109876, 5-129210, and 7-10665).
On the other hand, as described in the above reference (New Ceramics (7), pp.49-53, 1994), electrostatic attraction force is increased as volume resistivity (electrical resistivity) of an insulating layer is lowered, however, if too low, breakage of devices occurs due to leakage current. Therefore, it is considered that the volume resistivity of the insulating layer of the electrostatic holding apparatus is desirably 1010-1013 Ωcm.
However, in the case of using alumina for the insulating layer in the above wafer heating apparatus with electrostatic attraction function, the resistance value becomes too low in a medium and high temperature range of 500-800° C., resulting in a problem that breakage of devices occurs due to leakage current. In addition, in the case of using pyrolytic boron nitride for the insulating layer, the resistance value becomes too high in the above medium and high temperature range, resulting in another problem that sufficient electrostatic attraction force can not be obtained.
In order to solve such problems, there has been proposed an electrostatic holding apparatus using pyrolytic boron nitride containing carbon of 1-20% by weight for its insulating layer (see Japanese Patent Laid-Open (Kokai) No. 9-278527), which has a proper resistance value and sufficient electrostatic attraction force even in the medium and high temperature range of 500-800° C.
However, in the above heating apparatus with electrostatic attraction function, since an insulating layer composed of pyrolytic boron nitride is bonded onto a heating layer and an electrode for electrostatic attraction which are composed of pyrolytic graphite, they are weakly bonded by Van der Waals forces, resulting in a problem that delamination occurs in the bonding boundary portion by repeated rise and drop in temperature.
On the other hand, since rapid rise and rapid drop in temperature are essential to increase the throughput of wafers, a heating apparatus having a high resistance to thermal shock has been required.
Therefore, there has been expected development of a wafer heating apparatus having high reliability, which has a high thermal shock resistance and no problem of delamination, and which has a proper resistance value and sufficient electrostatic attraction force even in the medium and high temperature range of 500-800° C.